Ageing of equine articular cartilage: structure and composition of aggrecan and decorin

• Published in: Equine veterinary journal 1998, Vol.30 (1), p.43-52
• Main Authors: Platt, D, Bird, J.L.E, Bayliss, M.T
• Format: Article
• Language: English
• Subjects: age differences; ageing; aggrecan; Aggrecans; aging; Aging - metabolism; Animals; articular cartilage; cartilage; Cartilage, Articular - chemistry; Cartilage, Articular - metabolism; Chondroitin Sulfate Proteoglycans - analysis; Chondroitin Sulfate Proteoglycans - metabolism; Chondroitin Sulfates - analysis; Chondroitin Sulfates - metabolism; Chromatography, Ion Exchange - methods; Chromatography, Ion Exchange - veterinary; Decorin; DNA; DNA - analysis; DNA - metabolism; Electrophoresis, Polyacrylamide Gel - methods; Electrophoresis, Polyacrylamide Gel - veterinary; Extracellular Matrix Proteins; Female; glycosaminoglycans; homeostasis; horse; horses; Horses - metabolism; hyaluronic acid; Hyaluronic Acid - analysis; Hyaluronic Acid - metabolism; Immunoblotting - methods; Immunoblotting - veterinary; Lectins, C-Type; Male; proteoglycans; Proteoglycans - analysis; Proteoglycans - metabolism
• ISSN: 0425-1644; 2042-3306
• DOI: 10.1111/j.2042-3306.1998.tb04087.x

Summary In order to identify the pathological processes involved in the destruction of articular cartilage in arthritic diseases, it is first necessary to characterise the normal homeostasis of cartilage in a healthy joint. In particular, normal age‐related changes in the biochemistry of cartilage complicate any comparisons that are made between diseased and healthy tissue. There are, however, no reports in the literature detailing the influence of ageing on the biochemistry of proteoglycans in equine articular cartilage. This study addresses the absence of such information by investigating the structure of aggrecan and decorin extracted from a wide age‐range of full thickness equine tissue. The total glycosaminoglycan content of articular cartilage from the metacarpophalangeal joint remained relatively constant throughout life. In contrast, specific components such as hyaluronan increased in concentration with advancing age as did the content of a structural epitope present on keratan sulphate chains. There were also significant age‐related changes in the sulphation pattern of chondroitin sulphate chains. The structure of the large aggregating proteoglycan (aggrecan) became more heterogeneous in size with increasing age and each of the subspecies of aggrecan identified in the extracts was shown to carry a hyaluronan binding region (G1) domain. All subspecies of aggrecan also expressed specific epitopes to keratan sulphate, chondroitin‐4‐sulphate and chondroitin‐6‐sulphate glycosaminoglycan chains. The structure of the small nonaggregating proteoglycan decorin and the aggrecan stabilising molecule link protein were demonstrated to be similar in size and charge to that reported for other species.